Germany's Federal Archives have made 700,000 documents, photos, film footage and recordings of world war one available in a special section of its website.
Here are photos not just of the war zones but also of the social history of the time, the production of war-time industries and of other countries involved in the conflict.
All have detailed labels, captions and classifications to provide a comprehensive research tool not just for the idle historian but also for academics.
The films from numerous collections (each one is labelled with exact source) have been made available by the European Film Gateway, and have titles in both German and English. They can be searched by title or theme, for example the western front, the Turkish front, children, prisoners of war, the war in the mountains, the war at sea etc.
There is also a recording of Kaiser Wilhelm dated 6 August 1914, the day Austria-Hungary declared war on Russia and Serbia declared war on Germany.